Handgrip of Proficiency (3.5e Equipment)

From D&D Wiki

The Handgrip of Proficiency is a flexible sheathe just right for a sword handle, but which can adjust shape to handle anything from a crossbow to even a small nub on the gripping surface of any non-ammunition weapon. Once the grip is applied, it can be used. At will, as a swift action you may cast Master's Touch (Spell Compendium) on its attached weapon, thus gaining proficiency in it for 1 full minute.

Removing or adding a handgrip is a move action which provokes attacks of opportunity.